Vascular endothelial growth factor/vascular permeability factor (VEGF) is a family of approximately 15 kDa to 25 kDa proteins that are essential for angiogenesis in normal and tumor tissues. Tumor cells secrete VEGF to stimulate surrounding endothelium, thereby driving angiogenesis and supporting continued tumor growth and metastatic spread. inhibition of this process through the use of new molecular tools and drug discovery processes will be an important component of cancer therapeutic development. In Phase I, we plan to discover antagonists of VEGF by using combinatorial peptide libraries as sources of affinity ligands. Bacteriophage M13-displayed peptide libraries will be screened by affinity selection on VEGF isoforms and VEGF-related proteins. The identity of the binding peptides will be deduced by DNA sequencing and confirmed with synthetic peptides. Validation of peptide interaction with target will be through analysis of signal transduction pathways, receptor-binding assays, and effects on proliferation and migration of endothelial cells in culture, and on capillary formation in biological systems. In Phase II of the grant, peptide ligands and VEGF domains will be used to develop high throughput screens of combinatorial chemical compound libraries for the purpose of identifying low molecular weight chemical compounds that act by interfering with the process of angiogenesis and tumor growth. PROPOSED COMMERCIAL APPLICATIONS: Peptide ligands will be used as molecular probes in high throughput screening assays to identify small chemical compounds (leads) for drugs that inhibit activation of mitogenic signals or other responses of vascular endothelial growth factor receptor for the purpose of treating tumor growth and metastatic spread. We anticipate that some of the "hits obtained from our screening strategy will move on to preclinical animal testing.